Recently, in camera modules mounted on smartphones or the like, there has been an increasing number of camera modules incorporating a function of controlling the position of an imaging lens with high precision at high speed by detecting the position of the imaging lens and feeding back the position information. In particular, since high-precision hand blur correction is possible by introducing feedback control into optical image stabilization (OIS), it is expected that the number of cameras that adopt OIS, according to the growing demand for capturing distant subjects without blurring in dark places, will continue to increase in the future.
The hand blur in the cameras may be considered as an angular blur (or shake) in three directions of pitch, yaw, and roll. Generally, the pitch refers to a blur in a vertical direction with respect to an optical axis, the yaw refers to a blur in a horizontal direction with respect to the optical axis, and the roll refers to a rotational blur around the optical axis. Each blur amount is detected as an angular velocity signal by a gyro sensor, and is integrated to calculate an angular blur amount. In the cameras having the OIS function described above, OIS called a lens shift method or a barrel shift method becomes mainstream. In the OIS, hand blur is corrected by shifting the lens within the XY plane perpendicular to the optical axis depending on the angular blur amount in the pitch direction and the yaw direction. For the blur in the roll direction, so-called electronic hand blur correction which corrects it by signal processing is adopted in many cases.
A drive axis of an actuator, a position detection axis, a pixel direction axis of an imaging element, and the like in the camera module do not necessarily coincide with each other with respect to an angular velocity detection axis of the gyro sensor due to each mounting variation or the like. Therefore, certain signal correction (calibration) may be performed. In the case where the gyro sensor is mounted in a substrate of the camera module, a direction of the angular velocity detection axis may be detected by integral vibration, and a position detection signal may be corrected according to the direction of the angular velocity detection axis or an angular velocity detection signal may be corrected according to a drive direction of the actuator.
A technique of correcting an inclination between a shaking detection axis of an angular velocity sensor (gyro sensor) and a shaking correction axis of a drive system (actuator) is disclosed as the related art. Specifically, it is described that a correction signal of an angular velocity signal is obtained by using an inclination θ between the shaking detection axis and the shaking correction axis. As methods of obtaining the inclination θ, a method of measuring a mechanical angle and a method of actually giving an angular velocity (i.e., vibrating) are disclosed.
Similarly, a technique of correcting an output error based on the inclination of the installation angle of the angular velocity sensor is disclosed as the related art. Specifically, it is disclosed that an output error based on the inclination of the installation angle of the angular velocity sensor is corrected, and a correction factor is obtained from a ratio of outputs of the angular velocity sensor in two directions when vibration is applied in a predetermined axial direction.
Meanwhile, an example of a camera equipped with an acceleration sensor in addition to the angular velocity sensor in order to correct even a translation blur as well as the angular blur is disclosed as the related art. Specifically, it is disclosed that the angular velocity sensor and the acceleration sensor are mounted, and the translation blur is corrected together with the angle blur and a calculation amount of the translation blur is changed according to a posture of the camera.
However, it is very difficult to mechanically measure a direction of a detection axis within a packaged angular velocity sensor, and it is also time-consuming and cumbersome to apply vibration to the camera modules one by one during the manufacturing process of the camera modules.
Further, when the camera module and the angular velocity sensor are integrated, it may be possible to adopt a method of performing calibration by the integral vibration as described above, but when the camera module and the angular velocity sensor are separately mounted and then individually verified, calibration may be performed by establishing a certain criteria in each of the camera module and the angular velocity sensor, for example, when the maker that inspects the camera module is different from the maker that mounts the angular velocity sensor, or the like. However, such calibration is impossible using the integral vibration in the related art.